WARNING:  WHEN OPERATING THE AIRSTAIR FROM THE INTERIOR CONTROL PANEL, OPEN ENTRY DOOR TO COCKED POSITION TO ALLOW CLEAR VISIBILITY OF AREA OUTSIDE AIRPLANE TO PREVENT INJURY TO PERSONNEL. DO NOT OPEN DOOR BEYOND COCKED POSITION WHILE OPERATING AIRSTAIR OR EQUIPMENT MAY BE DAMAGED.

(3)  
Position interior standby control to RETRACT or exterior control to RETRACT and control switch to STANDBY position.

(a)  
Positioning of the controls to retract the airstair provides power to energize the retract relay of the stair motor which operates the airstair actuator. The actuator drives the

carriage pinions that cause the carriage to travel inboard on the rail assemblies. Ball bearing nuts attached to the upper ladder and driven by the ball screws attached to the carriage beams retract the upper ladder into the carriage.

(b)  
The initial motion of the airstair retract cycle causes the extend switch to move to the not-extend position which will illuminate the STAIRS OPERATING light on the interior control panel and cause the stair tread lights to go out.

(c)  
As the upper ladder begins to rotate up from the ground, the handrail mechanism within the upper ladder side rails will lower the handrails down against the ladders and the lower ladder will fold up under the upper ladder.

CAUTION:  NO SAFETY SWITCH IS PROVIDED IN THE STANDBY SYSTEM TO ENSURE THAT LOWER LADDER IS COMPLETELY FOLDED AGAINST UPPER LADDER BEFORE LADDER IS COMPLETELY RETRACTED INTO THE CARRIAGE.

(d)  
When the lower ladder has folded, the upper ladder retracts inboard into the carriage and the carriage retracts inboard on the rails until it reaches the limit of travel and the airstair retract switch is actuated. Actuation of the retract switch will stop the actuator motor and transfer power through the airstair door close switch, which is in the door not-closed position, to the door close relay. The airstair is prevented from moving while in the retracted position by the motor brake and is stabilized in flight by inflight supports.

(e)  
When the door close relay is energized, power is provided to operate the door motor, which rotates the door actuator. The actuator operates the door jackscrew connected to the door carriage. The door travels upward and outboard in the door and carriage tracks to the closed position. When the doorstops are seated properly, the door close switch is actuated to the closed position to stop the door actuator motor, and the STAIRS OPERATING light on the interior control panel will go out.

(4)  
When retract cycle is complete, position interior control to OFF or exterior control to the neutral position. Exterior selector switch will return to NORMAL position when released.

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52-61-0 Page 16  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  May 01/76 

NOTE:  If the forward entry door is open, the airstair door latch pin is not engaged and the AIRSTAIR door warning on the control cabin forward overhead panel will be illuminated. If the forward entry door is closed, returning the exterior control handle to the neutral position will automatically engage the airstair door latch pin and cause the AIRSTAIR door warning light to go out.
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Aug 15/68  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  52-61-0 Page 17 

FORWARD AIRSTAIR AND DOOR - TROUBLE SHOOTING
EFFECTIVITY
Standard Passenger Airplanes
1.  General
A.  The possible troubles for the forward airstairs are grouped into four charts: Door Opening, Airstair Extension, Airstair Retraction and Door Closing. Refer to the appropriate chart for trouble shooting a specific fault.
CAUTION:  IF AT ANY TIME DURING EXTENSION OR RETRACTION, CHATTERING OR ERRATIC OPERATION OCCURS, IMMEDIATELY DISCONNECT POWER FROM THE AIRSTAIR AND INVESTIGATE THE CAUSE.
B.  When trouble shooting the airstairs in NORMAL or STANDBY operation, the following conditions should be in effect:
(1)  
Power is on the airplane.

(2)  
The following forward airstair circuit breakers on the load control center are closed.

(a)  
Forward airstair control

(b)  
Forward airstair standby control

(c)  
Forward airstair actuator

(d)  
Forward airstair door

(e)  
Forward airstair door standby

(3)  
All electrical connections, particularly swing arm connectors, are checked to ensure proper mating and firm connections.

(a)  For access to area below airstair while stair is extended and drain pan is installed, remove two screws connecting swing arm bracket at aft rail and lay swing arm aft of hatch.
CAUTION:  DO NOT ATTEMPT TO MOVE SWING ARM OUT OF WAY OR USE SWING ARM AS HANDHOLD OR IT MAY BE DAMAGED.
　
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